This invention relates to a seal assembly for use in establishing a seal between two members, one of which reciprocates relative to the other. There is a wide range of mechanisms wherein a reciprocating member passes through the wall of a chamber or other fixed structure, and it is required to establish a seal between the chamber or structure and the reciprocating member to prevent leakage therebetween. This construction is commonplace in a wide variety of pumps, wherein a piston reciprocates in a cylinder, including down hole or lift pumps.
In such pumps, it is common to effect the reciprocating movement of the member from a crank or eccentric and thus it is not always possible to achieve pure straight line reciprocating movement. Also non-pure linear reciprocating movement can arise from normal misalignment between components that can arise from manufacturing tolerances, errors in installation, or movement or supports or foundations after installation.
This problem is encountered in pumps known as "hammer head pumps" used extensively in oil fields to pump crude oil from underground reservoirs. These pumps usually operate on a continuous basis and are frequently operated in large numbers in a single oil field. Accordingly, it is desirable to reduce the maintenance requirements of the pump to a minimum.
The existence of non-pure linear movement in such pumps can result in lateral loads on the components of the seal unit provided where the reciprocating member passes through the structure or through a guide. In oil field pumps, the loads on the reciprocating member are quite high having regard to the length thereof, which may be several thousand feet, in addition to the column of oil of similar length. Accordingly, any lateral misalignment develops a substantial side loading of the seal with a resultant high wear rate. It is therefore necessary to provide regular and costly maintenance of the seal or the inconvenience of leakage which may, amongst other things, cause adverse environmental conditions.
It is therefore the object of the present invention to provide a seal assembly for use in conjunction with reciprocating members that is tolerant to misalignment between the movable and stationary members so as to maintain an effective seal under such conditions and to provide a longer effective life.